Many clinical situations benefit from regulation of the vascular, lymphatic or duct systems by restricting the flow of body fluid or secretions. For example, the technique of embolization involves the introduction of particles into the circulation to occlude blood vessels, for example, so as to either arrest or prevent hemorrhaging or to cut off blood flow to a structure or organ. Temporary occlusion of blood vessels is desirable for managing various diseases and conditions.
In one example of an embolization procedure, local anesthesia is first given over a common artery. The artery is then percutaneously punctured and a catheter is inserted and fluoroscopically guided into the area of interest. An angiogram is then performed by injecting contrast agent through the catheter. An embolic agent is then deposited through the catheter. The embolic agent is chosen, for example, based on the size of the vessel to be occluded, the desired duration of occlusion, and/or the type of disease or condition to be treated (e.g., hypervascular tumors, uterine fibroids, etc.), among others factors. A follow-up angiogram may be performed to determine the specificity and completeness of the arterial occlusion. Blocking the blood supply to the tissue is intended to result in shrinkage and/or death of the tissue.
Embolic therapy is currently used to treat late stage liver cancer for patients that are not candidates for liver transplantation or liver resection. There are currently a number of specific embolic therapies available. These therapies include bland embolization, transarterial chemoembolization (TACE) and drug eluting bead (DEB) therapy.
Bland embolization utilizes embolic particles injected into arteries feeding the tumor to stop blood flow to the tumor, thus causing necrosis. The embolic particles do not contain a drug.
TACE involves initial localized injections of a chemotherapeutic drug followed immediately by injection of embolic particles to prevent drug reflux and to cause embolization. TACE provides two modes of action, embolization (necrosis) and chemotherapy, and it is more effective than BLAND embolization. However with TACE there is a lack of sustained drug release since it involves a single injection of a drug. In addition TACE is cumbersome to perform since it involves two separate steps in the procedure.
DEB combines the drug into the embolic particles and like TACE involves two modes of action. Unlike TACE, DEB offers the potential for sustained drug release. However, currently available DEB products show in-vitro rapid release (i.e., within hours) of the drug from the embolic particles. Also, current DEB therapy utilizes biostable particles so re-treatment is not possible. Clinically, DEB has been shown to be somewhat superior in efficiency to TACE. None of the embolic therapies is currently curative, although in a majority of cases a single therapy delays tumor progression.